An adaptive approach to edge detection using the transform domain and bandpass filtering is discussed. The method is also extended to 3-D and shown to yield better edge maps. The discrete symmetric cosine transform (DSCT) is shown to be the best transform for accurate edge detection. The theory is first discussed in 1-D. Then, the adaptive algorithm utilizing both the gradient and the Laplacian information is developed in 2-D and 3-D. Computer simulations with regular scenes and magnetic resonance imaging images are provided. The extension of the method to 3-D leads to improved noise immunity and better edge contours.